LibWeb: Re-implement HTML::Navigator using IDL

Get rid of the bespoke NavigatorObject class and use the modern IDL
strategies for creating platform objects to re-implement Navigator and
its associcated mixin interfaces. While we're here, implement it in a
way that brings WorkerNavigator up to spec :^)

Userland/Libraries/LibWeb/HTML/Navigator.cpp

@@ -0,0 +1,27 @@
+/*
+ * Copyright (c) 2022, Andrew Kaster <akaster@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibJS/Heap/Heap.h>
+#include <LibJS/Runtime/Realm.h>
+#include <LibWeb/Bindings/Intrinsics.h>
+#include <LibWeb/HTML/Navigator.h>
+
+namespace Web::HTML {
+
+JS::NonnullGCPtr<Navigator> Navigator::create(JS::Realm& realm)
+{
+    return *realm.heap().allocate<Navigator>(realm, realm);
+}
+
+Navigator::Navigator(JS::Realm& realm)
+    : PlatformObject(realm)
+{
+    set_prototype(&Bindings::cached_web_prototype(realm, "Navigator"));
+}
+
+Navigator::~Navigator() = default;
+
+}